spring security小结

Spring Security 主要实现了Authentication（认证，解决who are you? ） 和 Access Control（访问控制，也就是what are you allowed to do？，也称为Authorization）。Spring Security在架构上将认证与授权分离，并提供了扩展点。

核心对象：

SecurityContextHolder 是 SecurityContext的存放容器，默认使用ThreadLocal 存储，意味SecurityContext在相同线程中的方法都可用。

SecurityContext主要是存储应用的principal信息，在Spring Security中用Authentication 来表示。

获取principal：

Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal();

if (principal instanceof UserDetails) {
String username = ((UserDetails)principal).getUsername();
} else {
String username = principal.toString();
}

在Spring Security中，可以看一下Authentication定义：

public interface Authentication extends Principal, Serializable {

    Collection getAuthorities();

    /**
     * 通常是密码
     */
    Object getCredentials();

    /**
     * Stores additional details about the authentication request. These might be an IP
     * address, certificate serial number etc.
     */
    Object getDetails();

    /**
     * 用来标识是否已认证，如果使用用户名和密码登录,通常是用户名 
     */
    Object getPrincipal();

    /**
     * 是否已认证
     */
    boolean isAuthenticated();

    void setAuthenticated(boolean isAuthenticated) throws IllegalArgumentException;
}

在实际应用中，通常使用UsernamePasswordAuthenticationToken：

public abstract class AbstractAuthenticationToken implements Authentication,
        CredentialsContainer {
        }
public class UsernamePasswordAuthenticationToken extends AbstractAuthenticationToken {
}

一个常见的认证过程通常是这样的，创建一个UsernamePasswordAuthenticationToken，然后交给authenticationManager认证，

认证通过则通过SecurityContextHolder存放Authentication信息。

 UsernamePasswordAuthenticationToken authenticationToken =
            new UsernamePasswordAuthenticationToken(loginVM.getUsername(), loginVM.getPassword());

Authentication authentication = this.authenticationManager.authenticate(authenticationToken);
SecurityContextHolder.getContext().setAuthentication(authentication);

UserDetails 是Spring Security里的一个关键接口，用来表示一个principal。

public interface UserDetails extends Serializable {
    /**
     * 用户的授权信息，可以理解为角色
     */
    Collection getAuthorities();

    /**
     * 用户密码
     *
     * @return the password
     */
    String getPassword();

    /**
     * 用户名 
     *   */
    String getUsername();

    boolean isAccountNonExpired();  // 用户是否过期

    boolean isAccountNonLocked();  // 是否锁定

    boolean isCredentialsNonExpired(); // 用户密码是否过期

    boolean isEnabled(); // 账号是否可用
}

UserDetails提供了认证所需的必要信息，在实际使用里，可以自己实现UserDetails，并增加额外的信息，比如email、mobile等信息。

在Authentication中的principal通常是用户名，我们可以通过UserDetailsService来通过principal获取UserDetails：

public interface UserDetailsService {
    UserDetails loadUserByUsername(String username) throws UsernameNotFoundException;
}

小结

• SecurityContextHolder, 用来访问 SecurityContext.
• SecurityContext, 用来存储Authentication .
• Authentication, 代表凭证.
• GrantedAuthority, 代表权限.
• UserDetails, 对用户信息进行封装.
• UserDetailsService,对用户信息进行管理.

整个过程：

Authentication认证

1、用户进入登录页面，输入用户名和密码，security首先会进入UsernamePasswordAuthenticationFilter，调用

attemptAuthentication方法，将用户名和密码作为pricaipal和critial组合成UsernamePasswordAuthenticationToken实例

2、将令牌传递给AuthenticationManage实例进行验证，根据用户名查找到用户，在进行密码比对

3、校验成功后，会把查询到的user对象填充到authenticaton对象中，并将标志authenticated设为true

4、通过调用 SecurityContextHolder.getContext().setAuthentication(...) 建立安全上下文的实例，传递到返回的身份认证对象上

AbstractAuthenticationProcessingFilter 抽象类

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
			throws IOException, ServletException {

		HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) res;

		if (!requiresAuthentication(request, response)) {
			chain.doFilter(request, response);

			return;
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Request is to process authentication");
		}

		Authentication authResult;

		try {
			authResult = attemptAuthentication(request, response);
			if (authResult == null) {
				// return immediately as subclass has indicated that it hasn't completed
				// authentication
				return;
			}
			sessionStrategy.onAuthentication(authResult, request, response);
		}
		catch (InternalAuthenticationServiceException failed) {
			logger.error(
					"An internal error occurred while trying to authenticate the user.",
					failed);
			unsuccessfulAuthentication(request, response, failed);

			return;
		}
		catch (AuthenticationException failed) {
			// Authentication failed
			unsuccessfulAuthentication(request, response, failed);

			return;
		}

		// Authentication success
		if (continueChainBeforeSuccessfulAuthentication) {
			chain.doFilter(request, response);
		}

		successfulAuthentication(request, response, chain, authResult);
	}

调用requestsAuthentication()决定是否需要进行校验，如果需要验证，则会调用attemptAuthentication()进行校验，有三种结果：

1、验证成功，返回一个填充好的Authentication对象（通常带上authenticated=true），接着执行successfulAuthentication()

2、验证失败，抛出AuthenticationException，接着执行unsuccessfulAuthentication()

3、返回null，表示身份验证不完整。假设子类做了一些必要的工作（如重定向）来继续处理验证，方法将立即返回。假设后一个请求将被这种方法接收，其中返回的Authentication对象不为空。

AuthenticationException是运行时异常,它通常由应用程序按通用方式处理，用户代码通常不用特意被捕获和处理这个异常。

UsernamePasswordAuthenticationFilter（AbstractAuthenticationProcessingFilter的子类）

public Authentication attemptAuthentication(HttpServletRequest request,
			HttpServletResponse response) throws AuthenticationException {
		if (postOnly && !request.getMethod().equals("POST")) {
			throw new AuthenticationServiceException(
					"Authentication method not supported: " + request.getMethod());
		}

		String username = obtainUsername(request);
		String password = obtainPassword(request);

		if (username == null) {
			username = "";
		}

		if (password == null) {
			password = "";
		}

		username = username.trim();

		UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(
				username, password);

		// Allow subclasses to set the "details" property
		setDetails(request, authRequest);

		return this.getAuthenticationManager().authenticate(authRequest);
	}

attemptAuthentication () 方法将 request 中的 username 和 password 生成 UsernamePasswordAuthenticationToken 对象，用于 AuthenticationManager 的验证（即 this.getAuthenticationManager().authenticate(authRequest) ）

默认情况下注入 Spring 容器的 AuthenticationManager 是 ProviderManager。

ProviderManager（AuthenticationManager的实现类）

public Authentication authenticate(Authentication authentication)
			throws AuthenticationException {
		Class toTest = authentication.getClass();
		AuthenticationException lastException = null;
		Authentication result = null;
		boolean debug = logger.isDebugEnabled();

		for (AuthenticationProvider provider : getProviders()) {
			if (!provider.supports(toTest)) {
				continue;
			}

			if (debug) {
				logger.debug("Authentication attempt using "
						+ provider.getClass().getName());
			}

			try {
				result = provider.authenticate(authentication);

				if (result != null) {
					copyDetails(authentication, result);
					break;
				}
			}
			catch (AccountStatusException e) {
				prepareException(e, authentication);
				// SEC-546: Avoid polling additional providers if auth failure is due to
				// invalid account status
				throw e;
			}
			catch (InternalAuthenticationServiceException e) {
				prepareException(e, authentication);
				throw e;
			}
			catch (AuthenticationException e) {
				lastException = e;
			}
		}

		if (result == null && parent != null) {
			// Allow the parent to try.
			try {
                // 如果没有任何一个 Provider 验证成功，则使用父类型AuthenticationManager进行验证
				result = parent.authenticate(authentication);
			}
			catch (ProviderNotFoundException e) {
				// ignore as we will throw below if no other exception occurred prior to
				// calling parent and the parent
				// may throw ProviderNotFound even though a provider in the child already
				// handled the request
			}
			catch (AuthenticationException e) {
				lastException = e;
			}
		}

		if (result != null) {
            // 擦除敏感信息
			if (eraseCredentialsAfterAuthentication
					&& (result instanceof CredentialsContainer)) {
				// Authentication is complete. Remove credentials and other secret data
				// from authentication
				((CredentialsContainer) result).eraseCredentials();
			}

			eventPublisher.publishAuthenticationSuccess(result);
			return result;
		}

		// Parent was null, or didn't authenticate (or throw an exception).

		if (lastException == null) {
			lastException = new ProviderNotFoundException(messages.getMessage(
					"ProviderManager.providerNotFound",
					new Object[] { toTest.getName() },
					"No AuthenticationProvider found for {0}"));
		}

		prepareException(lastException, authentication);

		throw lastException;
	}

AuthenticationManager的默认实现是ProviderManager，它委托一组AuthenticationProvider实例来实现认证。
AuthenticationProvider和AuthenticationManager类似，都包含authenticate，但它有一个额外的方法supports，以允许查询调用方是否支持给定Authentication类型：

public interface AuthenticationProvider {

    Authentication authenticate(Authentication authentication)
            throws AuthenticationException;
    boolean supports(Class authentication);
}

ProviderManager包含一组AuthenticationProvider，执行authenticate时，遍历Providers，然后调用supports，如果支持，则执行遍历当前provider的authenticate方法，如果一个provider认证成功，则break。如果最后所有的 AuthenticationProviders 都没有成功验证 Authentication 对象，将抛出 AuthenticationException。

由 provider 来验证 authentication， 核心点方法是Authentication result = provider.authenticate(authentication);此处的 provider 是 AbstractUserDetailsAuthenticationProvider，它是AuthenticationProvider的实现，看看它的 authenticate(authentication) 方法

public Authentication authenticate(Authentication authentication)
			throws AuthenticationException {
        // 必须是UsernamePasswordAuthenticationToken
		Assert.isInstanceOf(UsernamePasswordAuthenticationToken.class, authentication,
				messages.getMessage(
						"AbstractUserDetailsAuthenticationProvider.onlySupports",
						"Only UsernamePasswordAuthenticationToken is supported"));

		// 获取用户名
		String username = (authentication.getPrincipal() == null) ? "NONE_PROVIDED"
				: authentication.getName();

		boolean cacheWasUsed = true;
        // 从缓存中获取
		UserDetails user = this.userCache.getUserFromCache(username);

		if (user == null) {
			cacheWasUsed = false;

			try {
                // retrieveUser抽象方法，获取用户
				user = retrieveUser(username,
						(UsernamePasswordAuthenticationToken) authentication);
			}
			catch (UsernameNotFoundException notFound) {
				logger.debug("User '" + username + "' not found");

				if (hideUserNotFoundExceptions) {
					throw new BadCredentialsException(messages.getMessage(
							"AbstractUserDetailsAuthenticationProvider.badCredentials",
							"Bad credentials"));
				}
				else {
					throw notFound;
				}
			}

			Assert.notNull(user,
					"retrieveUser returned null - a violation of the interface contract");
		}

		try {
            // 预先检查 DefaultPreAuthenticationChecks，检查用户是否被lock或者账号是否可用
			preAuthenticationChecks.check(user);
            // 抽象方法，自定义检验
			additionalAuthenticationChecks(user,
					(UsernamePasswordAuthenticationToken) authentication);
		}
		catch (AuthenticationException exception) {
			if (cacheWasUsed) {
				// There was a problem, so try again after checking
				// we're using latest data (i.e. not from the cache)
				cacheWasUsed = false;
				user = retrieveUser(username,
						(UsernamePasswordAuthenticationToken) authentication);
				preAuthenticationChecks.check(user);
				additionalAuthenticationChecks(user,
						(UsernamePasswordAuthenticationToken) authentication);
			}
			else {
				throw exception;
			}
		}
        // 后置检查 DefaultPostAuthenticationChecks，检查isCredentialsNonExpired
		postAuthenticationChecks.check(user);

		if (!cacheWasUsed) {
			this.userCache.putUserInCache(user);
		}

		Object principalToReturn = user;

		if (forcePrincipalAsString) {
			principalToReturn = user.getUsername();
		}

		return createSuccessAuthentication(principalToReturn, authentication, user);
	}

 三步验证工作
    1. preAuthenticationChecks
    2. additionalAuthenticationChecks（抽象方法，子类实现）
    3. postAuthenticationChecks

AbstractUserDetailsAuthenticationProvider 内置了缓存机制，从缓存中获取不到的 UserDetails 信息的话，就调用retrieveUser()方法获取用户信息，然后和用户传来的信息进行对比来判断是否验证成功。retrieveUser()方法在 DaoAuthenticationProvider 中实现， DaoAuthenticationProvider 是 AbstractUserDetailsAuthenticationProvider的子类。这个类的核心是让开发者提供UserDetailsService来获取UserDetails以及 PasswordEncoder来检验密码是否有效：

private UserDetailsService userDetailsService;
private PasswordEncoder passwordEncoder;

具体实现如下

protected final UserDetails retrieveUser(String username,
			UsernamePasswordAuthenticationToken authentication)
			throws AuthenticationException {
		UserDetails loadedUser;

		try {
			loadedUser = this.getUserDetailsService().loadUserByUsername(username);
		}
		catch (UsernameNotFoundException notFound) {
			if (authentication.getCredentials() != null) {
				String presentedPassword = authentication.getCredentials().toString();
				passwordEncoder.isPasswordValid(userNotFoundEncodedPassword,
						presentedPassword, null);
			}
			throw notFound;
		}
		catch (Exception repositoryProblem) {
			throw new InternalAuthenticationServiceException(
					repositoryProblem.getMessage(), repositoryProblem);
		}

		if (loadedUser == null) {
			throw new InternalAuthenticationServiceException(
					"UserDetailsService returned null, which is an interface contract violation");
		}
		return loadedUser;
	}

可以看到此处的返回对象 userDetails 是由 UserDetailsService 的 loadUserByUsername(username) 来获取的。

再来看验证：

protected void additionalAuthenticationChecks(UserDetails userDetails,
            UsernamePasswordAuthenticationToken authentication)
            throws AuthenticationException {
        Object salt = null;

        if (this.saltSource != null) {
            salt = this.saltSource.getSalt(userDetails);
        }

        if (authentication.getCredentials() == null) {
            logger.debug("Authentication failed: no credentials provided");

            throw new BadCredentialsException(messages.getMessage(
                    "AbstractUserDetailsAuthenticationProvider.badCredentials",
                    "Bad credentials"));
        }
        // 获取用户密码
        String presentedPassword = authentication.getCredentials().toString();
        // 比较passwordEncoder后的密码是否和userdetails的密码一致
        if (!passwordEncoder.isPasswordValid(userDetails.getPassword(),
                presentedPassword, salt)) {
            logger.debug("Authentication failed: password does not match stored value");

            throw new BadCredentialsException(messages.getMessage(
                    "AbstractUserDetailsAuthenticationProvider.badCredentials",
                    "Bad credentials"));
        }
    }

小结：要自定义认证，使用DaoAuthenticationProvider，只需要为其提供PasswordEncoder和UserDetailsService就可以了。

时序图

补充：SecurityContextHolder的工作原理

这是一个工具类，只提供一些静态方法，目的是用来保存应用程序中当前使用人的安全上下文。

缺省工作模式 MODE_THREADLOCAL

我们知道，一个应用同时可能有多个使用者，每个使用者对应不同的安全上下文，那么SecurityContextHolder是怎么保存这些安全上下文的呢 ？缺省情况下，SecurityContextHolder使用了ThreadLocal机制来保存每个使用者的安全上下文。这意味着，只要针对某个使用者的逻辑执行都是在同一个线程中进行，即使不在各个方法之间以参数的形式传递其安全上下文，各个方法也能通过SecurityContextHolder工具获取到该安全上下文。只要在处理完当前使用者的请求之后注意清除ThreadLocal中的安全上下文，这种使用ThreadLocal的方式是很安全的。当然在Spring Security中，这些工作已经被Spring Security自动处理，开发人员不用担心这一点。

SecurityContextHolder源码

public class SecurityContextHolder {
	// ~ Static fields/initializers
	// =====================================================================================

	public static final String MODE_THREADLOCAL = "MODE_THREADLOCAL";
	public static final String MODE_INHERITABLETHREADLOCAL = "MODE_INHERITABLETHREADLOCAL";
	public static final String MODE_GLOBAL = "MODE_GLOBAL";
	public static final String SYSTEM_PROPERTY = "spring.security.strategy";
	private static String strategyName = System.getProperty(SYSTEM_PROPERTY);
	private static SecurityContextHolderStrategy strategy;
	private static int initializeCount = 0;

	static {
		initialize();
	}

	// ~ Methods
	// ========================================================================================================

	/**
	 * Explicitly clears the context value from the current thread.
	 */
	public static void clearContext() {
		strategy.clearContext();
	}

	/**
	 * Obtain the current SecurityContext.
	 *
	 * @return the security context (never null)
	 */
	public static SecurityContext getContext() {
		return strategy.getContext();
	}

	/**
	 * Primarily for troubleshooting purposes, this method shows how many times the class
	 * has re-initialized its SecurityContextHolderStrategy.
	 *
	 * @return the count (should be one unless you've called
	 * {@link #setStrategyName(String)} to switch to an alternate strategy.
	 */
	public static int getInitializeCount() {
		return initializeCount;
	}

	private static void initialize() {
		if (!StringUtils.hasText(strategyName)) {
			// Set default
			strategyName = MODE_THREADLOCAL;
		}

		if (strategyName.equals(MODE_THREADLOCAL)) {
			strategy = new ThreadLocalSecurityContextHolderStrategy();
		}
		else if (strategyName.equals(MODE_INHERITABLETHREADLOCAL)) {
			strategy = new InheritableThreadLocalSecurityContextHolderStrategy();
		}
		else if (strategyName.equals(MODE_GLOBAL)) {
			strategy = new GlobalSecurityContextHolderStrategy();
		}
		else {
			// Try to load a custom strategy
			try {
				Class clazz = Class.forName(strategyName);
				Constructor customStrategy = clazz.getConstructor();
				strategy = (SecurityContextHolderStrategy) customStrategy.newInstance();
			}
			catch (Exception ex) {
				ReflectionUtils.handleReflectionException(ex);
			}
		}

		initializeCount++;
	}

	/**
	 * Associates a new SecurityContext with the current thread of execution.
	 *
	 * @param context the new SecurityContext (may not be null)
	 */
	public static void setContext(SecurityContext context) {
		strategy.setContext(context);
	}

	/**
	 * Changes the preferred strategy. Do NOT call this method more than once for
	 * a given JVM, as it will re-initialize the strategy and adversely affect any
	 * existing threads using the old strategy.
	 *
	 * @param strategyName the fully qualified class name of the strategy that should be
	 * used.
	 */
	public static void setStrategyName(String strategyName) {
		SecurityContextHolder.strategyName = strategyName;
		initialize();
	}

	/**
	 * Allows retrieval of the context strategy. See SEC-1188.
	 *
	 * @return the configured strategy for storing the security context.
	 */
	public static SecurityContextHolderStrategy getContextHolderStrategy() {
		return strategy;
	}

	/**
	 * Delegates the creation of a new, empty context to the configured strategy.
	 */
	public static SecurityContext createEmptyContext() {
		return strategy.createEmptyContext();
	}

	public String toString() {
		return "SecurityContextHolder[strategy='" + strategyName + "'; initializeCount="
				+ initializeCount + "]";
	}
}

Spring security获取当前用户

前面介绍过用SecurityContextHolder.getContext().getAuthentication() .getPrincipal();获取当前用户，还有一种方法：

经过spring security认证后，spring security会把一个SecurityContextImpl对象存储到session中，此对象中有当前用户的各种资料

SecurityContextImpl securityContextImpl = 
(SecurityContextImpl) request.getSession.getAttribute("SPRING_SECURITY_CONTEXT");
//登录名
System.out.println("Username:" + securityContextImpl.getAuthentication().getName());
//登录密码，未加密的
System.out.println("Credentials:" + securityContextImpl.getAuthentication().getCredentials());

SecurityContextImpl源码

/**
 * Base implementation of {@link SecurityContext}.
 * 

 * Used by default by {@link SecurityContextHolder} strategies.
 *
 * @author Ben Alex
 */
public class SecurityContextImpl implements SecurityContext {

	private static final long serialVersionUID = SpringSecurityCoreVersion.SERIAL_VERSION_UID;

	// ~ Instance fields
	// ================================================================================================

	private Authentication authentication;

	// ~ Methods
	// ========================================================================================================

	public boolean equals(Object obj) {
		if (obj instanceof SecurityContextImpl) {
			SecurityContextImpl test = (SecurityContextImpl) obj;

			if ((this.getAuthentication() == null) && (test.getAuthentication() == null)) {
				return true;
			}

			if ((this.getAuthentication() != null) && (test.getAuthentication() != null)
					&& this.getAuthentication().equals(test.getAuthentication())) {
				return true;
			}
		}

		return false;
	}

	public Authentication getAuthentication() {
		return authentication;
	}

	public int hashCode() {
		if (this.authentication == null) {
			return -1;
		}
		else {
			return this.authentication.hashCode();
		}
	}

	public void setAuthentication(Authentication authentication) {
		this.authentication = authentication;
	}

	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append(super.toString());

		if (this.authentication == null) {
			sb.append(": Null authentication");
		}
		else {
			sb.append(": Authentication: ").append(this.authentication);
		}

		return sb.toString();
	}
}

可以看出，主要就两个方法getAuthentication()和setAuthentication()

问题： 如果修改了登录用户的信息，怎么更新到security context中呢

目前想到的解决办法是重新认证：

//首先在WebSecurityConfig中注入AuthenticationManager
    @Bean
    @Override
    public AuthenticationManager authenticationManagerBean() throws Exception {
        return super.authenticationManagerBean();
    }
//在Controller中注入
    @Autowired
    private AuthenticationManager authenticationManager;
//接下来就是在会修改用户信息的地方设置重新认证
//也可以通过SecurityContextHolder获取
SecurityContextImpl securityContext = (SecurityContextImpl) request.getSession().getAttribute("SPRING_SECURITY_CONTEXT");
UsernamePasswordAuthenticationToken token = 
new UsernamePasswordAuthenticationToken(登录名,登录密码);
Authentication authentication = authenticationManager.authenticate(token);
//重新设置authentication
securityContext.setAuthentication(authentication);

因为我做的是前后端分离，返回的都是json格式的数据，所以在项目中还遇到的问题有：

利用SpringSecurity进行前后端分离的登录验证

spring security未登陆时，不跳转登陆页面改为返回JSON字符串

参考文章：

Spring Security入门（二）：基于数据库验证

Spring Security 架构与源码分析

Spring Security源码分析一：Spring Security认证过程